Re: [PATCH] powerpc/powernv/cpuidle: Pass correct drv->cpumask for registration

Vaidyanathan Srinivasan [off-list ref] writes:

* Michael Ellerman [off-list ref] [2017-03-20 14:05:39]:

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Vaidyanathan Srinivasan [off-list ref] writes:

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On powernv platform cpu_present could be less than cpu_possible
in cases where firmware detects the cpu, but it is not available
for OS.

It's entirely normal for present < possible, on my laptop for example,
so I don't see how that causes the bug.

Yes, present < possible in itself not a problem.  It is whether
cpu_device exist for that cpu or not.

...

Currently if CONFIG_HOTPLUG_CPU=n, then we skip calling register_cpu()
and that causes the problem.

...

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I really don't understand how a CPU not being present leads to a crash
in printf()? Something in that call chain should have checked that the
CPU was registered before crashing in printf() - surely?

Yes, we should have just failed to register the cpuidle driver.  I have
the fix here:

[PATCH] cpuidle: Validate cpu_dev in cpuidle_add_sysfs
http://patchwork.ozlabs.org/patch/740634/

OK. Can you send a v2 of this with a better change log that includes all
the clarifications above.

And despite your subject being powerpc/powernv/cpuidle, this is a
cpuidle patch. I can merge it, but I at least need you to Cc the cpuidle
maintainers so they have a chance to see it.

cheers